The term “stent” is generally used to refer to medical devices and/or supports therefore which can be implanted in anatomical passageways (e.g., blood vessels, valve annuluses, body ducts, etc.) of the body for the purpose of maintaining the patency or state of dilation of the passageway, reinforcing the passageway, or anchoring a valve or graft or other object within the passageway. For purposes of this application, the term “stent” is used to refer to such supports, including supports intended for radial expansion as well as supports which are not intended for radial expansion.
Many stents are not intended for delivery and subsequent expansion via catheter, but are instead delivered and deployed in their full form and shape. Examples of such stents include supports for surgical heart valves and grafts. Stents for delivery via catheterization may be initially disposed in a compact configuration of relatively small diameter upon or within a delivery catheter to facilitate insertion and advancement of the stent into a desired anatomical passageway. Once at the implantation site, such stents may be radially expanded to a larger diameter which is equal to or slightly larger than the diameter of the anatomical passageway in which the stent is to be implanted. When radially expanded to the larger diameter, the stent may be released from the delivery catheter, and left in place where it is anchored (e.g., via frictional engagement) to the surrounding wall of the anatomical passageway.
In general, expandable stents fall into two major categories: a) self-expanding and b) balloon-expandable. Self-expanding stents may be formed of resilient or shape memory material (e.g., spring steel or nitinol) which is capable of self-expanding from a relatively small delivery diameter to a larger deployed diameter, with the expansion being achieved by releasing the stent from its compressed configuration whereupon it expands to its larger diameter in spring-like fashion. Balloon-expandable stents may be formed of plastically deformable material (e.g., stainless steel) which can be radially expanded by inflating a balloon positioned within inner lumen of the stent.
Stents can be provided in various sizes and shapes. Many stents are simple cylindrical forms and have substantially constant diameters along their lengths. However, for some applications it may be desirable for a stent having a more complex shape, including shapes where the diameter of the stent varies substantially along the length of the stent.
Stent shapes can be defined using various techniques. One common device for shaping stents is a crimper. Current stent crimpers tend to be purely mechanized devices that crimp stent frames into basic geometric shapes such as constant-diameter cylinders and simple cones. They have relatively complex mechanisms but are limited to forming relatively simple shapes.
What are needed are crimping devices and methods for forming stents in complex shapes using a relatively simple forming mechanism. The current invention meets these needs.